Bojon's wisdom was light to me when I started pouring my musky tubes. I am a fan of woodturning, so turning concave plugs for my pvc pipes was not much of a problem. I spray canola oil into the pipe and revolve it at a 45 degree angle or so, then pour the surplus back into my pyrex cup. A few coats like this, and I get to the thickness I need. I usually go for 2 coats inside the pipe, let it cool down, take it out, and dip the front half of the tube in the pyrex cup. As many have mentioned, if you put that hot pipe under cold tap water, make absolutely sure no water touches the hot plastisol.